Social interaction and sensorimotor gating are disrupted in Schizophrenia and other psychiatric disorders. Recently, deficits in sensorimotor gating and social interaction were described in a mouse strain created by elimination of the Dishevelled-1 gene through gene targeting. Dishevelled-1 is a mammalian homolog of a highly-conserved cytoplasmic protein that is part of the Wnt signaling pathway, involved in cell-fate determination in virtually all eukaryotes. This and other evidence suggest that Dishevelled, and possibly the Wnt pathway more generally, may affect complex behavior by influencing either the development or the activity of cells within the adult central nervous system. To understand how this happens, it is necessary to identify proteins that interact with Dishevelled-1 in mammalian brain cells. At present, proteins that interact with Dishevelled remain entirely unknown. The mouse, while extremely tractable for genetic, neuroanatomic, and behavioral studies, is less well-suited to direct biochemical experimentation. The specific aims of this proposal are to identify proteins that interact with Dishevelled by taking advantage of the yeast two-hybrid system and the biochemically-tractable frog embryo. The Dishevelled protein from Xenopus laevis (African clawed frog) will be divided into subdomains that are highly conserved with Dishevelled-1 and with other Dishevelled homologs. Proteins that interact with these subdomains will be isolated from a Xenopus embryonic library, and their interactions with Dishevelled and the Wnt pathway studied in the Xenopus embryo. Mammalian homologs of confirmed Dishevelled-interactors will be identified by computerized search of the genetic databases, and obtained either from other investigators or by PCR from genetic libraries. These mammalian homologs will be tested for interaction with the corresponding mammalian Dishevelled proteins in the yeast and Xenopus systems. Polyclonal antibodies to Dishevelled- interactors will be generated and used to characterize their expression and developmental distribution in the mammalian central nervous system. Using the data obtained from Xenopus as a guide, alterations in the activity, processing, and localization of Dishevelled-interactors will be studied in the brains of both normal and Dishevelled-1 knock-out mice, with specific focus on brain regions, such as the nucleus accumbens, amygdala, and hippocampus, shown in other studies to be involved in sensorimotor gating and social affiliation. The developmental expression of Dishevelled-interactors will be characterized in human brain tissue, through collaboration with colleagues within the Department of Psychiatry at the University of Washington.